The present invention relates to orthodontic expansion devices in general and, more specifically, to those devices that utilize screw actuators to effect the expansion.
Screw expansion devices are well known in the orthodontic field to correct various dental abnormalities or occlusions. One of several types of orthodontic problems addressed by the present invention relates to an arch width or palate that is too narrow. This problem can also cause various other medical and dental difficulties. One general type of expansion device, commonly referred to as a rapid palatal expansion (RPE) device, includes a support apparatus having a screw mechanism. The support apparatus and screw mechanism are typically affixed to legs rigidly connected to teeth on opposite sides of the patient""s maxillary jaw. As the screw mechanism is rotated, an expansive force may be applied to the palate. Successive expansions over time deliver the necessary forces for widening the palate. These devices are often used on narrow palates of children while the jaw and other dental structure are in formative stages. For example, since the palate typically contains cartilage between the plates at earlier growth stages, palatal expanders are often a recommended course of treatment. It follows that the space available in the mouth of a child is relatively small and, therefore, size considerations and comfort issues become even more important in these cases.
Known orthopedic screw expansion devices are disclosed in U.S. Pat. Nos. 4,347,054; 5,002,485; and 5,281,133. As exemplified by these patents, expanders currently in commercial production include a screw unit for activation, four legs that are connected to molars and bicuspids of the patient and a supporting structure for maintaining structural integrity of the device. As also shown in these patents, the supporting structure of such typical devices may take up significant space within the mouth of a patient. Also, due to the size of the support structure, these devices cannot be situated at the uppermost arch region and cannot easily be used for mandibular expansion. U.S. Pat. No. 5,564,920 illustrates a palatal expander having a somewhat lower profile, however, the device is otherwise too complicated.
Another disadvantage of currently available orthodontic expanders is that the support structure can block the holes used for accepting a tool when actuating or turning the screw expander. Also, current expanders are typically substituted with a transpalatal arch after the expansion is complete to give the patient a more comfortable stabilizer at this stage of the treatment. Therefore, it has become apparent that improvements would be desirable in this general field to improve patient comfort and decrease any constraints on the use of such devices caused, for example, by the space consuming support structure. It would also be desirable to specifically reduce or even eliminate the need for substituting a palatal expander with a transpalatal arch.
The present invention therefore provides significant improvements in patient comfort by exhibiting a low profile and allowing installation closer to the patient""s palate. In particular, the expansion device of the present invention eliminates the bulky supports in past devices and therefore eliminates problems associated with those supports. The expansion device of this invention may also be used more readily for various orthodontic applications, such as palatal expansion or mandibular expansion, due to the lower profile of the device. Further advantages of the invention include the elimination or reduction in the need to replace the expansion device with a transpalatal arch after a palatal expansion and other improvements related to the streamlined design and reduction in costs typically associated with such devices.
In fulfillment of these and other advantages and objectives of the invention, one general type of orthodontic expansion device of this invention includes tubular-shaped screw actuating structure having respective oppositely threaded internal thread portions. The invention also generally includes first and second legs each having inner and outer ends with the outer ends being adapted for attachment to a patient""s teeth. Finally, in devices constructed in accordance with this embodiment of the invention, rod-shaped screw actuating structure is provided having respective oppositely threaded external thread portions in engagement with the internal thread portions of the tubular-shaped screw actuating structure. The tubular-shaped screw actuating structure and rod-shaped screw actuating structure cooperate to further connect the inner ends of the respective first and second legs such that rotation of at least one of the screw actuating structures moves the first and second legs toward or away from each other. In a more specific embodiment, the tubular-shaped screw actuating structure can comprise first and second tubular members each having one of the internal thread portions. In another similarly operating embodiment, the tubular-shaped screw actuating structure is a single piece structure and the oppositely threaded internal thread portions are threaded bores located at opposite ends of the single piece tubular-shaped structure.
When first and second threaded tubular members are used in the invention, the rod-shaped screw actuating structure may be a rod having a central tool engagement portion and having the external thread portions on opposite ends thereof in engagement with the respective internal thread portions of the first and second tubular members. On the other hand, when the tubular-shaped screw actuating structure is a single piece structure, the inner ends of the first and second legs can include the rod-shaped screw actuating structure. In each case, when the tool engagement portion is rotated through the use of an appropriate tool, such as with a piece of wire or a wrench, the two legs will move toward or away from each other.
As another manner of describing the invention, an embodiment of the orthodontic expansion device may comprise a screw element including first and second oppositely threaded end portions and a tool engagement portion disposed between the end portions. First and second legs extend in opposite directions from the screw element and each leg includes an inner end which is threaded and an outer end which is adapted for attachment to the teeth of a patient. The threaded inner ends of the legs are respectively engaged with the threaded end portions of the screw element such that rotation of the screw element in one direction will move the first and second legs away from each other while rotation of the screw element in an opposite direction will move the first and second legs toward each other.
As mentioned above, the threaded portions on the inner ends of the legs may be external threads or, in accordance with this embodiment, the threaded inner ends of the legs may be internal threads. In the latter case, the first and second oppositely threaded end portions on the screw element are external threads.
Additional advantages and objectives of the invention will become more apparent to those of ordinary skill upon review the following detailed description of the preferred embodiments taken in conjunction with the drawings.